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Old October 12th 19, 05:51 PM posted to rec.bicycles.tech
Andre Jute[_2_]
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Default Beginner question

On Saturday, October 12, 2019 at 2:28:00 PM UTC+1, AMuzi wrote:
On 10/11/2019 5:46 PM, Joy Beeson wrote:

It's been half a century since I needed the information, so I'm not
sure. Is a nineteen-inch bicycle frame nineteen inches from the
center of the bottom bracket to the center of the seat cluster?
"Center" defined as the middle of the top tube.

I measured my Fuji at 20.5 inches, and the guy I stole it from said
"twenty-one inches" sounded familiar.

To the top of the top tube seems more logical, since it's the
stand-over height one is interested in -- a fat-tube aluminum bike
would measure undersized if measured to the middle.

When I was thirty and forty and sixty I didn't mind that he's an inch
taller than me, but now that I'm seventy-nine, I've fallen over while
mounting twice, and think it's time to put the word out that I'm in
the market for an elderly bike that is compatible with my elderly
components.

But I have to say what size I want.


Engineering drawings show tube intersections and some brands
list dimensions all center to center, in this case center of
BB to center of top tube/seat tube joint.

A more common specification is a mix of tube centers (almost
all top tube specifications are center to center, like
wheelbase) and then seat tube size as BB center to top of
seat cluster. Why? I have no idea but that's the dominant spec.

Most road/tour frames list in centimeters, most offroad list
in inches. Why? I have no idea.

In our modern world, few frames have level top tubes (this
is generally a positive feature) so bicycle sales flacks
often list _two_ seat tube sizes, actual and what it would
be if the top tube were level. It's become so numbingly
complex that the better part of valor seems to be
XS-S-M-L-Xl which works very well (more sales, fewer knotted
eyebrows)

So much for discussion of theory after 100+ years of random
practice and flailing.

In our age group, I suggest you look at 'open' or 'ladies'
style frames in a medium size. Given the season, you'll get
some attention in a bike shop and as the saying goes it
doesn't cost to look. A test ride or two will also be useful
I think.

Note a few points:
1. There are not many mixtes made now. Get over it. Open
frames may be aesthetically different:
http://www.yellowjersey.org/WFDJHZ.JPG
http://www.yellowjersey.org/wfdopna2.jpg
but your flexibility and limberness probably won't improve
with time.
2. I assume you're looking at upright handlebars rather than
road (drop) bars. The large offroad market means you can
get matching quality compatible shifters for most popular
road gear systems. Flat or upright bars do not mean a lower
quality bike.
http://www.yellowjersey.org/nirofla2.jpg
3. Sporty looking bikes for younger people have low straight
handlebars. It's quick and cheap to add some height with a
handlebar swap. Bonus- riser bars adjust fore and aft with
an allen key in seconds.
4. If you have higher closer handlebars, more of your weight
shifts back, onto the saddle. Generally a wider saddle is
indicated AEBE.


And a shorter top tube. But I like the longer top tube because it keeps my size twelves out of the spokes. With a pair of North Road Bars (the Uno-Kalloy brand has served me well) and an adjustable stem you can adjust the height of the grips as well as your reach to the grips for the more upright position sensibly advised above, without sacrificing the desired wheelbase. -- AJ

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

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